Android. When a program is added programmatically, it doesn't show

I have a problem with my android app. I am trying to dynamically add a row to a TableLayout. Situation: When I click on a specific button, I want to add a row to the TableLayout, the text inside depends on what is being filled in some EditTexts.

This is part of my XML file:

<TableLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:stretchColumns="0,1"
                android:id="@+id/landenTable" 
                android:layout_height="wrap_content" 
                android:layout_width="match_parent">
</TableLayout>

      

        
        
        
      

    

Here is my Rekenmodel.java file:

public class Rekenmodel extends Activity{

    TableLayout landenTable;
    Data context = Data.GetInstance();
    String binnenUwRegio, selectedCountry, buitenUwRegio, naar085Bedrijfsnummers, naar088Bedrijfsnummers, naar0900Servicenummers, overigeGesprekken;
    Button b_send, b_addCountry;
    Spinner countries;
    EditText et_landen_aantalGesprekken, et_landen_bedrag;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.kpn_rekenmodel);
        landenTable = (TableLayout) findViewById(R.id.landenTable);
        countries = (Spinner) findViewById(R.id.countries);
        et_landen_aantalGesprekken = (EditText)this.findViewById(R.id.et_landen_aantalGesprekken);
        et_landen_bedrag = (EditText)this.findViewById(R.id.et_landen_bedrag);
        b_addCountry = (Button)this.findViewById(R.id.addCountryButton);
        b_addCountry.setOnClickListener(addCountryButtonListener);
    }

    private OnClickListener addCountryButtonListener = new OnClickListener() {

        @Override
        public void onClick(View v) {
            final TableRow tr = new TableRow(Rekenmodel.this);
            TextView landKeuze = new TextView(Rekenmodel.this);
            landKeuze.setText(countries.getSelectedItem().toString());
            landKeuze.setLayoutParams(new LinearLayout.LayoutParams(0, LayoutParams.WRAP_CONTENT, 0.45f));
            tr.addView(landKeuze);

            Button delete = new Button(Rekenmodel.this);
            delete.setLayoutParams(new LinearLayout.LayoutParams(0, LayoutParams.WRAP_CONTENT, 0.05f));
            delete.setText("Delete");
            delete.setTextSize(10f);
            delete.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    landenTable.removeView(tr);
                }
            });
            tr.addView(delete);

            TextView aantalGesprekken = new TextView(Rekenmodel.this);
            aantalGesprekken.setText(et_landen_aantalGesprekken.getText().toString());
            aantalGesprekken.setLayoutParams(new LinearLayout.LayoutParams(0, LayoutParams.WRAP_CONTENT, 0.15f));
            tr.addView(aantalGesprekken);

            TextView duur = new TextView(Rekenmodel.this);
            duur.setText("Test duur");
            duur.setLayoutParams(new LinearLayout.LayoutParams(0, LayoutParams.WRAP_CONTENT, 0.20f));
            tr.addView(duur);

            TextView bedrag = new TextView(Rekenmodel.this);
            bedrag.setText(et_landen_bedrag.getText().toString());
            bedrag.setLayoutParams(new LinearLayout.LayoutParams(0, LayoutParams.WRAP_CONTENT, 0.15f));
            tr.addView(bedrag);

            landenTable.addView(tr);
        }

    };
}